Learning Forum

[luna6362]

I am currently using a steady-state flow field combined with transient DPM particles.
I would like to understand the relationship between the iterations of the steady-state flow field and the time step size in the DPM model.
For example, how many iterations correspond to one DPM time step? How does DPM define time calculations under a steady-state simulation?
Are there any particular aspects I should pay attention to when simulating with a steady-state flow field combined with transient DPM?
Thank you!

[Rob]

DPM are tracked on their own time field, so you'll not see a "time" on the fluid side. You will see time on the particles. Basically, monitor values of interest (including total particle count) and wait for it to settle down. Do the particles alter the flow? 

[luna6362]

Hi Rob. I got it. Thank you for your reply! Happy New Year!!

There still have some questions here.

If I want to see the particles motion of each time step,how should I set the number of iters (Record every ? iters) at solution animations?

I assume that the particles won't change the flow.But when I choose "Unsteady particle tracking" ,it will force me to open "Interaction with continous phase".

And I am curious about how to calculate the particles num of every injection time step.

[Rob]

If the particles don't alter the flow you may want to explore Solution Controls > Equations as an approach. Just because we have to switch on interaction doesn't mean we have to solve the flow field......

That also resolves the animation as you can save every iteration or every some iterations to suit. Note, I always prefer to save images to build an animation later on. It's safer in that you can't lose a folder full of images and also means you can check what's going on during the run. I think everyone who's ever used animation has produced at least one of the residual plot by accident!  

[luna6362]

Is this the setting you mentioned earlier? (Apologies for the picture quality)

I cancelled the Flow in Equations box.

 

Yes, you're right. There are always mishaps when creating an animation.😆 Thank you for the reminder!

 

I still have some questions about DPM.

1. How can I determine which moment of the particle motion corresponds to the images at the iteration? 
2. Is the particle number for the face injection still calculated using the mesh of the face when employing transient DPM? (I only learned that the answer is yes when using steady DPM)

Thank you so much!

[Rob]

That's the one - turn the Turbulence & RSM equations off too. You're turning the flow solver off & just tracking particles. 

Parcel ID has a logical labelling method. What that method is isn't something I can explain! The number of parcels is the same as the number of surface facets and you're releasing a parcel per facet per time step. 

There isn't a good link between iteration and particle position as it's down to the flight time: that's then a function of the DPM time step. Saving images with %i in the name will add the iteration number to the filename (%t is flow time step & %f is flow time). 

 

[luna6362]

I understand! There is one last question. Sorry for so many questions.😢

I have set escape faces and trap faces in the model.

How can I calculate the mass flow rate of particles that escape during the entire simulation process?

I only learned that I can track the mass flow rate of each DPM time step by choosing "Summary" in the Particle Tracks panel.

But I need to see the total mass flow rate of escaped particles.

Thank you so much!

[Rob]

I very much doubt it'll be the last question... ;)  

Look in the Reports (tree in Fluent) as there's a DPM Report for mass flow in there. You can then report mass, you'll need to do the sums afterwards as it's per iteration data. 

[luna6362]

I don't think it will be the last question either!🤣 I'll take a look at the DPM report.

As always, thank you so much for answering everyone's questions.

Hoping you have a fantastic New Year!🌠

[Rob]

:)    Have a look for Columbo, a TV detective played by Peter Falk: "Just one more thing.....".  

You're welcome, Happy New Year.